There are significant applications for electronic apparatus, such as a radio transmitter, wherein it is desired to provide a plurality of outputs at different power levels. One such application is in marine radio equipment wherein the maximum power which can be transmitted when the boat is in port is only one watt, but a larger power output, such as six watts, is desired when the boat is at sea. Radio transmitters normally provide a low power output at some stage in the power amplifier system which may be at the proper level for the "in port" output. However, this low power output is not easily available for application to the antenna of the radio. To provide the connections and circuit conductors for connection of the low power output to the antenna requires substantial room which may not be available in the radio housing. Also the connection must provide matched impedances to conduct the radio frequency signals with low power loss. Accordingly, it is difficult to provide a circuit arrangement for adapting a small portable transmitter, such as the transmitter of a handheld two-way radio, for such "low power-high power" operation.
Although the state of the art makes it possible to initiate the design of a new radio transmitter which has low power and high power outputs which are selectively transmitted, the cost of such a new design is substantial and might not be easily justified by the number of radios of this type that will be used. For this reason, it is desired to provide a compact circuit arrangement for adapting an existing radio transmitter for "low power-high power" operation.